1. Field of the Invention
This invention relates to door interlocks, and in particular to door interlocks for use in microwave ovens for effecting concurrently latching of the door in a closed position and potentiation of the control for the microwave energy generating means to permit energization thereof only when the door is in the closed and latched condition.
2. Description of the Prior Art
In the conventional microwave oven, a microwave energy generating device is provided for delivering microwave energy into a cavity defined by a cabinet having a front opening selectively closed by a door. To prevent leakage of the microwave energy from the cavity during operation of the oven, it is important to positively prevent access to the oven cavity when the microwave energy generating means is energized so as to prevent injury to the user. Thus, it is conventional to provide interlocking means for assuring that the cabinet door is in the closed and latched position before the microwave energy generating means may be energized. A number of different interlocking systems have been developed to provide such functioning. The present invention is concerned with an improved form of such a system.
One form of such interlocking system in an electronic oven is shown in U.S. Letters Pat. No. 3,339,054 of Homer W. Deaton, wherein the control includes timer operated switches, a holding circuit including a momentary switch, a safety interlock switch, a safety switch, a door switch, and a thermostat switch.
Shiro Umezu et al disclose in U.S. Letters Pat. No. 3,699,299 a locking member for locking the door in the closed position. A switch is disposed in the cabinet for controlling operation of the microwave energy generator, and means interlocked with the handle are provided for operating the switch to de-energize the generator when the locking device releases the door.
Shiro Umezu et al, in U.S. Letters Pat. No. 3,715,554, disclose the use in such a microwave oven of a locking mechanism for holding the door in the closed position including a handle connected to the locking mechanism and a switch mounted on the cabinet. The switch is interlocked with the locking mechanism for controlling operation of the generator when the door is locked and unlocked by the locking mechanism.
Shiro Umezu et al, in U.S. Letters Pat. No. 3,715,552, show a microwave oven wherein the door locking mechanism comprises an operating member mounted on the door outside the heating chamber, a switch in the cabinet, and means interlocked with the locking mechanism for operating the switch for de-energizing the generator when the operating member is operated to unlock the locking mechanism.
In U.S. Pat. No. 3,777,098 of William R. Tapper, a door latch assembly for use in a microwave oven is disclosed as having a latch element carried by the oven door and a latch receiving element mounted on the oven cabinet. The latch receiving element includes a first, fixed aperture for receiving an aligning projection of the latch element, and a movable body having a pair of apertures receiving hooked latch portions of the latch element. The movable body includes a pair of ported plates having bearing surfaces adapted to be moved by the latches. The latches extend into the plate ports after a preselected movement thereof and are secured therein by a pair of leaf springs which move the plates and body upwardly in a secured position. A safety switch is connected to each port plate and is controlled by the hooked portions of the latches.
In U.S. Pat. No. 3,816,688 of Rex E. Fritts, a safety interlock system for microwave ovens is shown having means for interrupting the power supply and/or actuating a failure indicating device. The sensing means is arranged so as to not carry the load current until a malfunction of a companion interlock occurs.
Takeshi Takayama et al, in U.S. Pat. 3,823,294, show a door interlocking system having a solenoid operated contactor with the solenoid thereof switched by at least two switching means, one of which is manually operable and the other of which is operated by operation of the lock means acting upon the door which, in turn, is operated by a drive coil connected with the power supply through one of the switching means.
In U.S. Pat. No. 3,865,097, Donald B. Robinson discloses a latch for microwave ovens provided with a plate mounted on the oven door with means on the oven cabinet for receiving the latch. A switch holder assembly and a slide bar are mounted on the cabinet with the switch holder assembly being stationary and the slide bar being actuated by an actuating bar, or button, accessible on the front face of the oven. A latch receiving element is pivotally supported between the switch holder assembly and the actuating slide bar for engagement by the latches so that when the oven door is closed and the slide bar is actuated against its normal upward biasing, the latch receiving element pivotally disengages from the latch and the door is permitted to open.
Rex E. Fritts discloses in his Re. No. 28,822, a safety interlock system for a microwave oven incorporating sensor means for detecting any malfunction. The sensing means are associated with interlocks and the sensing means, as in Fritts' U.S. Pat. No. 3,816,688, do not carry the normal load current until a malfunction of the companion interlock occurs.